A method to estimate the timing of linear enamel hypoplasia for Neandertals

1Department of Anthropology, University of Illinois at Urbana-Champaign, 2Department of Anthropology, The Ohio State University, 3Department of Oral Biology, University of Newcastle, 4Department of Anthropology, The University of North Carolina at Chapel Hill, 5Department of Human Evolutionary Biology, Harvard University

During childhood, systemic physiological stresses such as illness, disease, and malnutrition can disturb the growth of dental enamel. These disruptions are often recorded in the form of linear enamel hypoplasia (LEH). Many researchers have analyzed the frequency and timing of LEH formation in Neandertal populations as they relate to ideas about Neandertal living conditions, nutrition, and foraging efficiency. Previous age estimates for Neandertal LEH were largely based upon modern human dental growth standards. However, recent studies provide a more complete picture of Neandertal tooth formation. We used data from these studies to create enamel growth charts for four Neandertal anterior tooth types (upper central and lateral incisors, upper and lower canines), which are analogous to those created for modern humans by Reid and Dean (2000). The Neandertal charts differ from modern humans in the average age span encompassed by enamel formation and in the duration of enamel formation within equivalent divisions of crown height. These differences result because Neandertal teeth initiated at earlier ages, have shorter cuspal enamel formation times, have lower average long-period line periodicities (mode 7 and 8 days), and exhibit a more uniform distribution of perikymata across their enamel surfaces. Based on these new charts, we aged a series of Krapina Neandertal defects calculated from both modal long-period periodicities. The median ages at defect formation across different anterior tooth types range from 2.3-2.5 (7-day periodicity) to 2.6-2.8 years (8-day periodicity), suggesting that Neandertals experienced physiological stress earlier in life than previous estimates derived from modern human standards.